diff mbox series

[v2,07/12] parisc/percpu: Work around the lack of __SIZEOF_INT128__

Message ID 20230601101409.GS4253@hirez.programming.kicks-ass.net
State New
Headers show
Series None | expand

Commit Message

Peter Zijlstra June 1, 2023, 10:14 a.m. UTC 
On Wed, May 31, 2023 at 04:21:22PM +0200, Arnd Bergmann wrote:

> It would be nice to have the hack more localized to parisc
> and guarded with a CONFIG_GCC_VERSION check so we can kill
> it off in the future, once we drop either gcc-10 or parisc
> support.

I vote for dropping parisc -- it's the only 64bit arch that doesn't have
sane atomics.

Anyway, the below seems to work -- build tested with GCC-10.1

---
Subject: parisc/percpu: Work around the lack of __SIZEOF_INT128__
From: Peter Zijlstra <peterz@infradead.org>
Date: Tue May 30 22:27:40 CEST 2023

HPPA64 is unique in not providing __SIZEOF_INT128__ across all
supported compilers, specifically it only started doing this with
GCC-11.

Since the per-cpu ops are universally availably, and
this_cpu_{,try_}cmpxchg128() is expected to be available on all 64bit
architectures a wee bodge is in order.

Sadly, while C reverts to memcpy() for assignment of POD types, it does
not revert to memcmp() for for equality. Therefore frob that manually.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 arch/parisc/include/asm/percpu.h |   77 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 77 insertions(+)

Comments

Peter Zijlstra June 2, 2023, 2:39 p.m. UTC | #1 
On Thu, Jun 01, 2023 at 09:29:18AM -0400, Linus Torvalds wrote:

> Right now we have that "minimum gcc version" in a somewhat annoying
> place: it's in the ./scripts/min-tool-version.sh file as a shell
> script.

Something like so then?

---
Subject: parisc: Raise minimal GCC version
From: Peter Zijlstra <peterz@infradead.org>
Date: Fri Jun  2 16:33:54 CEST 2023

With 64bit builds depending on __SIZEOF_INT128__ raise the parisc
minimum compiler version to gcc-11.0.0.

All other 64bit architectures provide this from GCC-5.1.0 (and
probably before), except hppa64 which only started advertising this
with GCC-11.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 scripts/min-tool-version.sh |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

--- a/scripts/min-tool-version.sh
+++ b/scripts/min-tool-version.sh
@@ -17,7 +17,11 @@ binutils)
 	echo 2.25.0
 	;;
 gcc)
-	echo 5.1.0
+	if [ "$SRCARCH" = parisc ]; then
+		echo 11.0.0
+	else
+		echo 5.1.0
+	fi
 	;;
 llvm)
 	if [ "$SRCARCH" = s390 ]; then
Mark Rutland June 2, 2023, 2:50 p.m. UTC | #2 
On Fri, Jun 02, 2023 at 04:39:12PM +0200, Peter Zijlstra wrote:
> On Thu, Jun 01, 2023 at 09:29:18AM -0400, Linus Torvalds wrote:
> 
> > Right now we have that "minimum gcc version" in a somewhat annoying
> > place: it's in the ./scripts/min-tool-version.sh file as a shell
> > script.
> 
> Something like so then?
> 
> ---
> Subject: parisc: Raise minimal GCC version
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Fri Jun  2 16:33:54 CEST 2023
> 
> With 64bit builds depending on __SIZEOF_INT128__ raise the parisc
> minimum compiler version to gcc-11.0.0.
> 
> All other 64bit architectures provide this from GCC-5.1.0 (and
> probably before), except hppa64 which only started advertising this
> with GCC-11.
> 
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> ---
>  scripts/min-tool-version.sh |    6 +++++-
>  1 file changed, 5 insertions(+), 1 deletion(-)
> 
> --- a/scripts/min-tool-version.sh
> +++ b/scripts/min-tool-version.sh
> @@ -17,7 +17,11 @@ binutils)
>  	echo 2.25.0
>  	;;
>  gcc)
> -	echo 5.1.0
> +	if [ "$SRCARCH" = parisc ]; then
> +		echo 11.0.0
> +	else
> +		echo 5.1.0
> +	fi
>  	;;
>  llvm)
>  	if [ "$SRCARCH" = s390 ]; then

I gave this a spin and it looks good to me:

[mark@lakrids:~/src/linux]% usekorg 10.3.0 make ARCH=arm64 CROSS_COMPILE=aarch64-linux- defconfig
  HOSTCC  scripts/basic/fixdep
  HOSTCC  scripts/kconfig/conf.o
  HOSTCC  scripts/kconfig/confdata.o
  HOSTCC  scripts/kconfig/expr.o
  LEX     scripts/kconfig/lexer.lex.c
  YACC    scripts/kconfig/parser.tab.[ch]
  HOSTCC  scripts/kconfig/lexer.lex.o
  HOSTCC  scripts/kconfig/menu.o
  HOSTCC  scripts/kconfig/parser.tab.o
  HOSTCC  scripts/kconfig/preprocess.o
  HOSTCC  scripts/kconfig/symbol.o
  HOSTCC  scripts/kconfig/util.o
  HOSTLD  scripts/kconfig/conf
*** Default configuration is based on 'defconfig'
#
# configuration written to .config
#
[mark@lakrids:~/src/linux]% usekorg 10.3.0 make ARCH=parisc CROSS_COMPILE=hppa64-linux- generic-64bit_defconfig
***
*** C compiler is too old.
***   Your GCC version:    10.3.0
***   Minimum GCC version: 11.0.0
***
scripts/Kconfig.include:44: Sorry, this C compiler is not supported.
make[1]: *** [scripts/kconfig/Makefile:94: generic-64bit_defconfig] Error 1
make: *** [Makefile:692: generic-64bit_defconfig] Error 2
[mark@lakrids:~/src/linux]% usekorg 11.3.0 make ARCH=parisc CROSS_COMPILE=hppa64-linux- generic-64bit_defconfig
#
# configuration written to .config
#

FWIW:

Tested-by: Mark Rutland <mark.rutland@arm.com>

Mark.
Linus Torvalds June 2, 2023, 4:09 p.m. UTC | #3 
On Fri, Jun 2, 2023 at 10:40 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> Something like so then?

Ack. I think it would be much cleaner if we would have it as part of
the Kconfig file and architectures could just override some
GCC_MIN_VERSION value, but that's not the universe we currently have,
so your patch looks like the best thing to do.

              Linus
H. Peter Anvin June 2, 2023, 5 p.m. UTC | #4 
On June 2, 2023 7:39:12 AM PDT, Peter Zijlstra <peterz@infradead.org> wrote:
>On Thu, Jun 01, 2023 at 09:29:18AM -0400, Linus Torvalds wrote:
>
>> Right now we have that "minimum gcc version" in a somewhat annoying
>> place: it's in the ./scripts/min-tool-version.sh file as a shell
>> script.
>
>Something like so then?
>
>---
>Subject: parisc: Raise minimal GCC version
>From: Peter Zijlstra <peterz@infradead.org>
>Date: Fri Jun  2 16:33:54 CEST 2023
>
>With 64bit builds depending on __SIZEOF_INT128__ raise the parisc
>minimum compiler version to gcc-11.0.0.
>
>All other 64bit architectures provide this from GCC-5.1.0 (and
>probably before), except hppa64 which only started advertising this
>with GCC-11.
>
>Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
>---
> scripts/min-tool-version.sh |    6 +++++-
> 1 file changed, 5 insertions(+), 1 deletion(-)
>
>--- a/scripts/min-tool-version.sh
>+++ b/scripts/min-tool-version.sh
>@@ -17,7 +17,11 @@ binutils)
> 	echo 2.25.0
> 	;;
> gcc)
>-	echo 5.1.0
>+	if [ "$SRCARCH" = parisc ]; then
>+		echo 11.0.0
>+	else
>+		echo 5.1.0
>+	fi
> 	;;
> llvm)
> 	if [ "$SRCARCH" = s390 ]; then

Dumb question: is this only about the cpp macro or is it about __int128 existing at all?
Peter Zijlstra June 2, 2023, 7:10 p.m. UTC | #5 
On Fri, Jun 02, 2023 at 10:00:17AM -0700, H. Peter Anvin wrote:

> Dumb question: is this only about the cpp macro or is it about __int128 existing at all?

It's mostly about __int128 being there, __SIZEOF_INT128__ is just the
way we go about detecting if it's there or not.
H. Peter Anvin June 2, 2023, 7:20 p.m. UTC | #6 
Ok. So the patch description needs to be fixed. Otherwise the solution would be far simpler :)
Peter Zijlstra June 2, 2023, 7:40 p.m. UTC | #7 
On Fri, Jun 02, 2023 at 12:20:05PM -0700, H. Peter Anvin wrote:
> Ok. So the patch description needs to be fixed. Otherwise the solution would be far simpler :)

"With 64bit builds depending on __SIZEOF_INT128__ to detect the
presence of __int128 raise the parisc minimum compiler version to
gcc-11.0.0."

better?
Linus Torvalds June 2, 2023, 7:57 p.m. UTC | #8 
On Fri, Jun 2, 2023 at 3:40 PM Peter Zijlstra <peterz@infradead.org> wrote:
>
> "With 64bit builds depending on __SIZEOF_INT128__ to detect the
> presence of __int128 raise the parisc minimum compiler version to
> gcc-11.0.0."
>
> better?

I'd just say "64-bit targets need the __int128 type, which for pa-risc
means raising the minimum gcc version to 11".

The __SIZEOF_INT128__ part isn't the important part. That's just the symptom.

               Linus
Helge Deller June 2, 2023, 8:42 p.m. UTC | #9 
On 6/2/23 16:39, Peter Zijlstra wrote:
> On Thu, Jun 01, 2023 at 09:29:18AM -0400, Linus Torvalds wrote:
>
>> Right now we have that "minimum gcc version" in a somewhat annoying
>> place: it's in the ./scripts/min-tool-version.sh file as a shell
>> script.
>
> Something like so then?
>
> ---
> Subject: parisc: Raise minimal GCC version
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Fri Jun  2 16:33:54 CEST 2023
>
> With 64bit builds depending on __SIZEOF_INT128__ raise the parisc
> minimum compiler version to gcc-11.0.0.
>
> All other 64bit architectures provide this from GCC-5.1.0 (and
> probably before), except hppa64 which only started advertising this
> with GCC-11.
>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>

The patch raises the compiler for 32- and 64-bit parisc builds, but that's OK.

So:
Acked-by: Helge Deller <deller@gmx.de>

Thank you!
Helge


> ---
>   scripts/min-tool-version.sh |    6 +++++-
>   1 file changed, 5 insertions(+), 1 deletion(-)
>
> --- a/scripts/min-tool-version.sh
> +++ b/scripts/min-tool-version.sh
> @@ -17,7 +17,11 @@ binutils)
>   	echo 2.25.0
>   	;;
>   gcc)
> -	echo 5.1.0
> +	if [ "$SRCARCH" = parisc ]; then
> +		echo 11.0.0
> +	else
> +		echo 5.1.0
> +	fi
>   	;;
>   llvm)
>   	if [ "$SRCARCH" = s390 ]; then
diff mbox series

Patch

--- /dev/null
+++ b/arch/parisc/include/asm/percpu.h
@@ -0,0 +1,77 @@ 
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_PARISC_PERCPU_H
+#define _ASM_PARISC_PERCPU_H
+
+#include <linux/types.h>
+
+#if defined(CONFIG_64BIT) && CONFIG_GCC_VERSION < 1100000
+
+/*
+ * GCC prior to 11 does not provide __SIZEOF_INT128__ on HPPA64
+ * as such we need to provide an alternative implementation of
+ * {raw,this}_cpu_{,try_}cmpxchg128().
+ *
+ * This obviously doesn't function as u128 should, but for the purpose
+ * of per-cpu cmpxchg128 it might just do.
+ */
+typedef struct {
+	u64 a, b;
+} u128 __attribute__((aligned(16)));
+
+#define raw_cpu_generic_try_cmpxchg_memcmp(pcp, ovalp, nval)		\
+({									\
+	typeof(pcp) *__p = raw_cpu_ptr(&(pcp));				\
+	typeof(pcp) __val = *__p, __old = *(ovalp);			\
+	bool __ret;							\
+	if (!__builtin_memcmp(&__val, &__old, sizeof(pcp))) {		\
+		*__p = nval;						\
+		__ret = true;						\
+	} else {							\
+		*(ovalp) = __val;					\
+		__ret = false;						\
+	}								\
+	__ret;								\
+})
+
+#define raw_cpu_generic_cmpxchg_memcmp(pcp, oval, nval)			\
+({									\
+	typeof(pcp) __old = (oval);					\
+	raw_cpu_generic_try_cmpxchg_memcpy(pcp, &__old, nval);		\
+	__old;								\
+})
+
+#define raw_cpu_cmpxchg128(pcp, oval, nval) \
+	raw_cpu_generic_cmpxchg_memcmp(pcp, oval, nval)
+#define raw_cpu_try_cmpxchg128(pcp, ovalp, nval) \
+	raw_cpu_generic_try_cmpxchg_memcmp(pcp, ovalp, nval)
+
+#define this_cpu_generic_try_cmpxchg_memcmp(pcp, ovalp, nval)		\
+({									\
+	bool __ret;							\
+	unsigned long __flags;						\
+	raw_local_irq_save(__flags);					\
+	__ret = raw_cpu_generic_try_cmpxchg_memcmp(pcp, ovalp, nval);	\
+	raw_local_irq_restore(__flags);					\
+	__ret;								\
+})
+
+#define this_cpu_generic_cmpxchg_memcmp(pcp, oval, nval)		\
+({									\
+	typeof(pcp) __ret;						\
+	unsigned long __flags;						\
+	raw_local_irq_save(__flags);					\
+	__ret = raw_cpu_generic_cmpxchg_memcmp(pcp, oval, nval);	\
+	raw_local_irq_restore(__flags);					\
+	__ret;								\
+})
+
+#define this_cpu_cmpxchg128(pcp, oval, nval) \
+	this_cpu_generic_cmpxchg_memcmp(pcp, oval, nval)
+#define this_cpu_try_cmpxchg128(pcp, ovalp, nval) \
+	this_cpu_generic_try_cmpxchg_memcmp(pcp, ovalp, nval)
+
+#endif /* !__SIZEOF_INT128__ */
+
+#include <asm-generic/percpu.h>
+
+#endif /* _ASM_PARISC_PERCPU_H */